1. Calculate the acceleration:

* We know the initial velocity (vi = 2.4 m/s), final velocity (vf = 4.9 m/s), and time (t = 0.5 s).

* Use the formula: acceleration (a) = (vf - vi) / t

* a = (4.9 m/s - 2.4 m/s) / 0.5 s = 5 m/s²

2. Calculate the change in speed over 2.5 seconds:

* Use the formula: change in velocity (Δv) = acceleration (a) * time (t)

* Δv = 5 m/s² * 2.5 s = 12.5 m/s

Answer: The speed changes by 12.5 m/s in 2.5 seconds.